Aniline123 most important notes for exams.pdf

Notes

1. ANILINE
Mol.formula-C
6H
5NH
2
NH
2

2. PreparationofAniline
1.Fromnitrobenzene
Anilineispreparedbyreducingnitrobenzeneinthepresenceoftinandconc.HCl.
NO
2 NH
2
+6[H] +2H
2O
Nitrobenzene Aniline
2.Fromphenol
PhenolsreactwithammoniainthepresenceofZnCl2at300
0
cunderpressureto
giveaniline.
+H
2O
Sn/HCl
OH
ZnCl
2/300
0
c
pressure
NH
2

3. Physicalproperties
1.Itiscolourlessliquidwithunpleasantodourandverysensitiveto
oxidation,soitrapidlybecomesbrownwhenexposedtoair.
2.Itsboilingpointis184
0
candsolidifiesat-6.2
0
c.
3.Itissparinglysolubleinwaterbutsolubleinorganicsolvents.
4.Itissteamvolatileandpoisonous.

4. Resonating structure of Aniline

5. Anilineislessbasicthanammonia
Inaniline,-NH
2groupisattachedwithphenylgroupwhichisan
electronwithdrawinggroup.Duetowhichphenylgroupdecreases
electrondensityatN-atommakinglessavailabilityfordonation.
Henceanilineislessbasicthanammonia.

6. Chemicalproperties
A.Reactiondueto–NH2group
1.Basicnature
NH
2 NH
3Cl
+HCl
Aniliniumchloride

7. 2.Alkylation
Anilinereactwithalkylhalidetogivemixtureofsecondary,tertiaryand
quaternaryammoniumcompound.
NH2 NHCH3 N(CH
3)
2 N(CH
3)
3I
+CH3l
−��
??????�??????�??????�??????�
-HI
N-methyl aniline N,N-dimethyl aniline Trimethylaniliniumiodide

8. 3.Acylation
Anilineundergoesacylationwhentreatedwithacidchlorideoracid
anhydridetogiveanilides.
NH2 NHCOCH 3
+CH3COCl +HCl
N-phenylethanamide(acetanilide)
NH2 NHCOC
6H
5
+ C6H5COCl + HCl
N-phenyl benzamide (benzanilide)
????????????????????????�????????????�
????????????????????????�????????????�

9. 4 . Carbylaminereaction
NH2 NC
+CHCl3 +3KCl+3H2O
phenylcarbalyamineorphenylisocyanide
5.Condensationwitharomaticaldehyde
Anilineonwarmingwithbenzaldehydeformsbenzylideneaniline,
knownasSchiff’sbase.
NH2+O=CH N=CH +H2O
Benzylideneaniline(Benzalaniline)
alcKOH

10. 7.Diazotizationreaction
Whenanilineistreatedwithnitrousacid(ormixtureofNaNO
2+HCl)at0-5°C,
diazoniumsaltisformed.Thisprocessofconvertingprimaryaromaticamineintoa
diazoniumcompoundisknownasdiazotizationreaction.
NH
2 N
2Cl
+2H
2O
Aniline Benzenediazoniumchloride
+ HNO
2
NaNO
2/HCl
0-5
0
c

11. 8.Couplingreaction
Anilinecoupleswithbenzenediazoniumchlorideinslightlyacidicmediumto
formp-aminoazobenzene(orange-yellowdye).
p-aminoazobenzene(orange-yellowdye)
-N=NCl+ H- -NH
2
Acidic medium
-N=N- -NH
2
+ HCl

12. B.Reactionduetoring
-NH
2groupinanilineiso-pdirectorandstronglyactivatinggroup.
1.Halogenation
Anilinereactswithaq.brominetogivewhiteppt.of2,4,6-tribromoaniline.
NH
2 NH
2
+Br
2(aq.) +3HBr
Aniline
2,4,6-tribromoaniline(whiteppt.)
Br Br
Br

13. Inpresenceofnonpolarsolvent(CS
2)itgivesmonosubstitutedproduct.
NH
2 NH
2
+Br
2 +HBr
Aniline
p-bromoaniline
CS
2
Br

14. 2.Nitration
Why–NH
2(amino)groupofanilineisprotectedbeforenitration?
Conc.nitricacidbeingnitratingagent,itisalsostrongoxidizingagent.So
itoxidizesanilineintodifferentoxidizingproductsandcangivepolynitrated
products.Thereforeaminogroupisprotectedbeforenitration.Protectionis
carriedoutbytreatingitwithacetylchlorideandthennitrationisdone.
–NH
2groupisregeneratedbyhydrolysis.
NH
2 NHCOCH
3 NHCOCH
3 NH
2
+CH
3COOH
Acetanilide
p-nitroaniline
CH
3COCl
pyridine
Conc.HNO
3
Conc.H
2SO
4
H
2O/H
+
NO
2 NO
2

15. 3.Sulphonation
Anilineonsulphonationat200
0
cgivessulphanilicacid.
NH
2 NH
3HSO
4 NH
2
Conc.H
2SO
4
200
0
C
SO
3H
(Sulphanilicacid)
Anilinium
hydrogensulphate
p-aminobenzenesulphonicacid